We plan to study two groups of 5-8 adolescent chimpanzees, each group living in a 1 1/2-acre enclosure partially simulating a natural habitat. The initial focus will be on the adaptation of each group to its new environment. Thereafter the principal focus will be on changes in behavior that occur during adolescence and beyond, noting sex differences and individual differences. We will especially focus on changes in behavior in the sphere of aggression, sex, and attachment, and hormonal correlates of these behavior patterns. We expect to delineate these patterns, to measure changes in their frequency and duration over the years of adolescence, and to search for endocrine correlates. We will differentiate such behavior patterns by aage, sex, phase of menstrual cycle, hormonal condition as occurring spontaneously and as manipulated experimentally, and environmental conditions. Our semi-natural chimpanzee facility will permit repeated endocrine measures over several years; the administration of hormones for experimental purposes; continuous, close-range observation of behavior; a simple social system focusing on peer relations; systematic comparison of behavior in this semi-natural habitat with behavior of chimpanzees in their fully natural habitat and with human adolescents in roughly similar situations. Hormone assays will be conducted on a regular basis over the next two years including measurement of several androgens, estrogen, progesterone, the gonadotropin LH, and biogenic amines. The research will be conducted by an interdisciplinary group: ethnology, psychiatry, biochemistry, statistics, and sociology. There will be a long-term, collaborative arrangement between the Stanford research and a longitudinal study of chimpanzees behavior in the natural habitat in Tanzania.